Vacuum systems for manufacturing integrated circuits on wafers are generally known. Several vacuum chambers usually comprise a single vacuum system. A vacuum processing system may typically have a centralized vacuum chamber, called a transfer chamber, which may be part of a mainframe. As the name implies, a transfer chamber's primary purpose is to transfer wafers between other chambers. Other chambers may include process chambers, cool-down chambers, buffer chambers and load lock chambers, among others. A vacuum processing system may also have some kind of subsystem, such as a mini-environment, for delivering wafers to the load lock chambers and removing the wafers from the load lock chambers so the wafers can be moved to the next system for additional processing. This transfer chamber plus the peripheral chambers and staging areas are sometimes called a cluster tool.
Access between chambers is provided through a slit valve. A slit valve includes an opening in a chamber where another chamber's slit valve opening is attached in order for wafers, or substrates, to be passed between the two chambers. Typically, a slit valve opening is an elongated rectangle through which a substrate can pass. The match between the slit valves of two chambers must be airtight in order to maintain the vacuum within the system.
A typical transfer chamber has six slit valves since it is passing wafers between other chambers. A process chamber typically only has one slit valve.
The actual opening for a slit valve in the side of some chambers, like a transfer chamber, is typically a generic rectangular hole that doesn't actually match up with the slit valve of any chamber. Thus, a slit valve insert typically is inserted into the transfer chamber's generic opening in order to match the transfer chamber's opening with the process chamber's specific opening. The insert has an opening matching the process chamber to which it is to be attached. In other words, a slit valve insert is an adapter between chambers.
Additionally, different process chambers have openings of different shapes and sizes. Therefore, different slit valve inserts may be used in the same transfer chamber's slit valve openings.
FIG. 1 shows an example of a slit valve insert 2 immediately before it is inserted into or after it is removed from slit valve opening 26 of transfer chamber 12. Insert 2 has an opening 4 through which wafers are passed and a front surface 5 for pressing against a process chamber. The process chamber will have a wafer-access opening, or slit valve opening, matching opening 4 and usually forms an airtight seal with a surface around its wafer-access opening that matches front surface 5. Insert 2 also has a channel 6 around the opening 4. Channel 6 aligns with a mating surface on the process chamber and holds an O-ring for sealing with the process chamber.
Slit valve inserts have been inserted into a transfer chamber's openings from the outside of the chamber as shown by FIG. 1. The process chamber is then attached over the insert and holds the insert firmly in place. The slit valve provides access between chambers. An actuating cylinder disposed through the floor of the transfer chamber closes the slit valve with a slit valve door that seats on a surface around the slit valve opening. The seat for the door is disposed within the transfer chamber. The slit valve opening, insert, door and actuating cylinder form the slit valve.
The opening and closing cycles of the slit valve will slowly cause the door and the insert to wear out or become dirty or contaminated. A worn out or dirty door or insert may lead to leaks between the transfer chamber and the process chamber, perhaps allowing toxic gases to escape from the process chamber to the transfer chamber or allowing gases from the transfer chamber to enter the process chamber and reduce the process chamber's vacuum capability. A problem occurs if a slit valve insert becomes dirty and needs to be cleaned or becomes worn out and needs to be replaced. Since the inserts are mounted between the transfer chamber and the process chambers from the outside of the transfer chamber, the process chambers have to be completely removed to replace the inserts. Removing and reattaching a process chamber can be a very time-consuming task.
One solution would be to have the inserts inserted from the inside of the transfer chamber because then the chamber openings would have to be redesigned in order to provide such access and in order to make sure that the insert will still form a proper airtight seal with the process chamber. One difficulty with a redesign to accommodate inserting an insert from the inside of the chamber would require that the shoulder used to stop the insert after it has slid into the opening be machined from the inside of the transfer chamber, a very difficult process.
Thus, a need has arisen for a vacuum manufacturing system with a transfer chamber that has a slit valve insert that can be selected to attach to any process chamber and that can be serviced from the inside of the transfer chamber without redesigning the chamber.